Study on corrosion behavior of low carbon steel under different water conditions in bentonite of China-Mock-Up

Abstract In China-Mock-Up, the transition of water conditions in bentonite and its influence on the corrosion behavior of four low carbon steel electrochemical sensors buried in bentonite along horizontal direction were investigated by in situ electrochemical impedance spectroscopy (EIS) with the infiltration of groundwater from outside to inside. The results show that in the initial stage of EIS measurement, water in bentonite around the electrochemical sensors from outside to inside is hygroscopic water and chemical bonding water successively. With increasing time, water in the outer bentonite transforms from hygroscopic water to free water. Meanwhile, water in the inner bentonite transforms from chemical bonding water to hygroscopic water. As water in bentonite exists as the chemical bonding water, the equivalent circuit can be described as a pure capacitor, which does not cause the corrosion of low carbon steel. When water in bentonite exists as hygroscopic water, it can be described as a circuit consisting of two leakage capacitors in series, which causes the slight corrosion of the steel. While, in the presence of free water, the equivalent circuit can be described as a free water resistance and two leakage capacitors in series, which causes the serious corrosion of the steel.